CAMSHAFT ASSEMBLY SUPPORT STRUCTURE
A camshaft assembly support structure includes two camshaft assemblies including two shafts parallel to each other and cam pieces fitted on an outer surface of each of the two shafts, support members independent from each other and each including two bearings receiving the two shafts, the bearings each having a bearing surface seamless over an entire inner circumference, and positioning members each having a through hole receiving and tightly holding the shaft. The positioning members are positioned on both sides of each of the support members to position the support members in the axial direction of the shafts with the shafts being received in the bearings.
This application claims priority from Japanese Patent Applications No. 2019-049714 filed on Mar. 18, 2019 and No. 2019-200595 filed on Nov. 5, 2019. The entire contents of the priority application are incorporated herein by reference.
TECHNICAL FIELDThe present invention relates to a camshaft assembly support structure.
BACKGROUNDA known camshaft assembly support structure (hereinafter, a support structure) includes a camshaft assembly and a support member supporting the camshaft assembly. In the support structure of this type, the support member includes multiple bearings (journal bearings) that support the journals of the camshaft assembly. The camshaft assembly is supported by the multiple bearings arranged in the axial direction. For example, Japanese Unexamined Patent Application Publication No. 2008-157062 describes a support member of this type. The support member is a solid (single) member in which each of the bearing holes, which receive a journal, has a seamless inner surface over the entire circumference. In the solid support member, the shaft center is less likely to be displaced and a lubricant oil is more likely to be uniformly distributed over the inner surface of the bearing than in a support member including a bearing constituted of separate upper and lower portions. The support structure is eventually fixed to a cylinder head of an internal combustion engine, for example, by bolting.
SUMMARYIn the support member of the known technology, bearings are connected to each other by a frame located around the bearings and are arranged in lines. When a camshaft assembly is attached to the support member, multiple cam pieces need to be fixed to the shaft at the same time, for example, by shrink-fitting, with the shaft of the camshaft assembly being received by the bearing of the support member. Thus, it is difficult to attach the camshaft to the known support member. Furthermore, the frame of the support member may limit the space for the attachment operation of the cam pieces to the shaft. For example, when the cam pieces are fixed to the shaft by shrink-fitting, it may be difficult to position a jig for holding the cam piece near the bearing.
An object of the technology described herein is to provide a camshaft assembly support structure including a camshaft assembly and a support member that are readily assembled.
A camshaft assembly support structure includes two camshaft assemblies, support members, and positioning members. The camshaft assemblies include two shafts parallel to each other and multiple cam pieces fitted on outer surfaces of the shafts. The support members are independent from each other. The support members include bearings having bearing surfaces. Each of the support members includes two of the bearings receiving the shafts, respectively. Each of the bearing surfaces is seamless over an entire inner circumference of each of the bearings. The positioning members include through holes in which the shafts are fitted and tightly hold the shafts. The positioning members are disposed on both sides of each of the support members to position the support members in an axial direction of the shafts with the shafts being received in the bearings.
The technology described herein provides a camshaft assembly support structure including a camshaft assembly and a support member that are readily assembled.
A first embodiment of the invention is described with reference to
In this specification, in some cases, one of the camshaft assemblies 2 that is on the upper side in
The camshaft assembly 2 includes a shaft 21 and multiple cam pieces (cam lobes) 22 fitted on an outer surface of the shaft 21. The support structure 1 of this embodiment, which includes the two camshaft assemblies 2, includes two shafts 21 and the cam pieces (cam lobs) 22 fitted on the outer surface of each of the shafts 21. In this specification, in some cases, the shaft 21 of the camshaft assembly 2A on the upper side in
The shaft 21 is formed by processing a metal material into a rod-like overall shape. The two shafts 21 supported by the support members 3 are arranged parallel to each other. As illustrated in
As illustrated in
The bearing 32 is a journal bearing and rotatably supports the shaft 21 (journal) with the shaft 21 (journal) being received in the hole 32a. The inner surface 32b of the hole 32a is seamless over the entire circumference.
The support structure 1 includes multiple positioning members 4. As illustrated in
To position the support member 3 on the left in
In other words, two positioning members 4 are disposed adjacent to one side surface (left side in
The positioning members 4 do not need to be in close contact with the support member 3. A space may be left between the support member 3 and the positioning member 4 as long as the movement of the support member 3 on the shafts 21 in the axial direction is limited to some extent. The space between the support member 3 and the positioning member 4 absorbs a dimension error when the support structure 1 is attached to a predetermined portion of a cylinder head.
Next, with reference to
Next, as illustrated in
Then, as illustrated in
After the cam pieces 22 are attached to the shafts 21, as illustrated in
As described above, the support structure 1 of this embodiment is produced by sequentially attaching the positioning members 4, the support member 3, the positioning members 4, the cam pieces 22, and the other components to the two shafts 21 from one end to the other end. In the support structure 1 having such a configuration, the camshaft assemblies 2 and the support members 3 are readily assembled. The support members 3 are each positioned in the axial direction of the camshaft assembly 2 (shaft 21) by the positioning members 4 positioned on the both sides of the support member 3. The support structure 1 having such a configuration is easy to transport and is also easy to eventually attach to a cylinder head.
Furthermore, in the support structure 1 of the embodiment, the support members 3 are independent from each other and not connected to each other. Thus, a space for jigs, which hold the positioning members 4 or the cam pieces 22, is readily provided around the shafts 21.
Although not illustrated in the drawings, the end portion of the shaft 21 (camshaft assembly 2) has a sprocket on which a timing belt, which transmits rotary motion of the crankshaft, is to be wound.
The support structure 1 of this embodiment is eventually fixed to a cylinder head by bolting.
The diameter R1 of the bolt through hole 31a (dimension in the axis L direction in
The technology disclosed herein is not limited to the embodiment described above and with reference to the drawings. The following embodiments may be included in the technical scope of the present technology.
(1) In the above-described embodiment, the positioning members 4 have a ring-like shape, but the present technology is not limited to this. The positioning members 4 may have any shape that has a hole to receive the shaft and can position the support member.
(2) In the above-described embodiment, the positioning member 4 and the cam piece 22 are different members independent from each other. However, the present technology is not limited to this configuration. In some embodiments, for example, as illustrated in
(3) In the above-described embodiment, the positioning members 4 are used to position the support member 3 relative to the shafts 21. However, in some embodiments, after the attachment position accuracy of the positioning members 4 on the both sides of the support member 3 in the axial direction is improved, the positioning members 4 may be used to position (cam thrust) the camshaft assembly 2 in the axial direction (axis L direction) relative to the cylinder head.
Claims
1. A camshaft assembly support structure comprising:
- two camshaft assemblies including two shafts parallel to each other and a plurality of cam pieces fitted on outer surfaces of the shafts;
- support members being independent from each other and including bearings having bearing surfaces, each of the support members including two of the bearings receiving the shafts, respectively, each of the bearing surfaces being seamless over an entire inner circumference of each of the bearings; and
- positioning members including through holes in which the shafts are fitted and tightly holding the shafts, the positioning members being disposed on both sides of each of the support members to position the support members in an axial direction of the shafts with the shafts being received in the bearings.
2. The camshaft assembly support structure according to claim 1, wherein
- the support members have bolt through holes through which bolts are inserted, and
- the bolts in the bolt through holes include projecting ends that project from the bolt through holes and are to be screwed into screw holes in a cylinder head to attach the camshaft assembly support structure to the cylinder head.
3. The camshaft assembly support structure according to claim 2, wherein positions of the screws holes, positions of the bolt through holes, spaces between the support members and the positioning members on the both sides of the support members in the axial direction, and spaces between the bolts and the bolt through holes in the axial direction are defined to satisfy a relation expressed by where Xa is a position error of each of screw holes in the axial direction of the shafts, Xb is a position error of each of the bolt through holes in the axial direction, Xc is each of the space between each of the support members and each of the positioning members on either side of the each of the support members in the axial direction, and Xd is each of the spaces between each of the bolts and corresponding one of the bolt through holes in the axial direction.
- Xd>Xa+Xb+Xc
4. The camshaft assembly support structure according to claim 1, wherein each of the cam pieces fitted on the outer surfaces of the shafts and one of the positioning members adjacent to the each of the cam pieces are portions of a single solid component.
Type: Application
Filed: Feb 18, 2020
Publication Date: Sep 24, 2020
Inventor: Manabu SHIBATA (Nishio-shi)
Application Number: 16/793,707